1. Field of the Invention
The present invention relates to a camera lens assembly, and more particularly to a camera lens assembly that enables a lens assembly installed in a digital camera, a mobile communication terminal or the like to be supported in an initial position and to be displaceable in the direction of an optical axis when the lens assembly is driven.
2. Description of the Related Art
With the recent developments in manufacturing technology of digital cameras, a miniaturized and light-weight camera lens assembly has been introduced, and a camera device has been installed in a mobile communication terminal. A mobile communication terminal equipped with an optical lens and a camera device is generally becoming very popular.
The performance of the camera device installed in the mobile communication terminal at the initial stage, when the camera device began to be installed in mobile communication terminals, was at a much lower level as compared with that of a digital camera which was already commercialized at that time. For example, the performance of the digital camera of a cheap model was generally four megapixels, while the performance of the camera device installed in a mobile communication terminal was typically 300 thousands pixels, and a camera device installed in a deluxe model mobile communication terminal was generally not more than one megapixel.
However, in recent years it has become popular to install a camera device with one megapixel in mobile communication terminals. For the deluxe model mobile communication terminal a camera device having three megapixels has been installed, which corresponds to performance of a cheap model digital camera. A mobile communication terminal having a camera device with the performance of more than seven megapixels has now been commercialized. As such, the improvement in a camera function of the mobile communication terminal is owed to the improvement in the precision of manufacturing technologies of the camera lens assembly.
The focal length of a camera lens module refers to a distance between a lens and an imaging surface, which will vary based upon the distance between the lens and an object to be photographed. Therefore, in order to obtain the best resolution of images, it is required to vary the distance between the lens module and an image sensor depending on the distance to the object to be photographed. Particularly, in a case where a high quality image with high resolution is required, it is necessary to install a device for compensating the focal length. A device for performing such a compensation of the focal length may be divided into two types: a manual focus compensation device in which a user manually corrects the focal length, and an automatic focus compensation device in which the focal length is automatically corrected by a device provided in the lens module.
FIG. 1 is a schematic sectional view illustrating a state where the focal length is corrected according to the movement of the lens module of a conventional camera lens assembly. FIG. 2 is a schematic sectional view illustrating a state where the focal length is corrected according to the movement of a lens in the lens module of the conventional camera lens assembly.
As shown in FIG. 1, when a lens module 11 is displaceable in its entirety in a camera lens assembly 10, there is no change in the structure of the lens module 11. Therefore, since there is no change in the characteristics of an optical system except for the change of the focal length according to the movement of the lens module 11, this construction is usually adopted and used in the structure of the camera assembly 10 having a simple construction.
However, a camera assembly 10 has recently been provided with a variety of additional functions such as an electric-powered shutter or an optical zoom, so that the interconnection within the camera lens module 11 becomes more complicated. Accordingly, it becomes difficult to drive the lens module 11 as a whole unit. Furthermore, since the lens module 11 has to be driven in its entirety, it has a drawback in that a driving force is needed to drive the lens module 11.
In order to solve the above drawbacks, there has been adopted a method in which at least one of the lenses provided in the lens module 21 of the camera lens assembly 20 is driven so as to vary the focal length, as shown in FIG. 2. In this manner, it is advantageous in that such a method requires relatively less driving force since at least one of the lenses 22 provided in the lens module 21 needs to be driven.
However, this still has drawbacks in that the optical characteristics such as an optical magnification rate may be changed upon the movement of the lens 22 because at least one of the lenses 22 provided in the lens module 21 needs driving.
Further, since a drive mechanism for driving the lens has to be inserted within the lens module, it is difficult to miniaturize the drive mechanism when it is to be installed in a portable terminal, a small camera or the like.
Meanwhile, another method for driving the camera lens module is disclosed in Korean Patent Application No. 2007-35155 filed on Apr. 10, 2007 by the assignee of this invention.
As shown in FIG. 3, the camera lens module 30 includes a driving part 34. The driving part 34 is installed on one side of a lens module 33 so that the lens module 33 can be displaceable back and forth in the direction of an optical axis O. A guiding part is provided between the lens module 33 and the driving part 34. The lens module 33 includes at least one lens therein and adjusts the focal length of the lens while moving back and forth in the direction of the optical axis O. The lens module 33 is supported by an upper and a lower leaf spring 35 provided within a housing 31. A magnetic substance 34a is mounted on one side of the lens module 3. The magnetic substance 34a faces a coil 34b provided at one side of the housing 31 and cooperates with the coil 34b to produce a driving force to move the lens module 33 back and forth. When an electric current is applied to the coil 34b, the coil 34b generates an electric field. The electric field generated by the coil 34b and the magnetic field of the magnetic substance 34a cooperate with each other, so that they produce a driving force to push or retract the lens module 33.
The camera lens assembly described above has a complicated structure since the leaf spring is secured to the housing. In addition, a distortion is generated when the position of the camera lens assembly is altered or an impact is exerted thereto. It also has a drawback that the housing becomes bigger since a space for mounting and moving the leaf spring should be provided at an upper and lower side of the lens assembly in order to install the leaf spring.
As such, there has been a need to develop a camera lens assembly that can be miniaturized for a mobile communication device, portable electronic equipment or the like in accordance with current trends of making such devices thinner.
Furthermore, as for a camera lens assembly installed in a mobile communication device or the like, there has been a need to develop a camera lens assembly that can support the lens assembly in an initial position within the housing when not driven, while it can not only be resiliently deformed according to the movement of the lens assembly in the direction of the optical axis, but also be designed to restore the lens assembly to its initial position when driven.